The first objective is to provide a simple and effective caries preventive regime for cancer patients suffering from xerostomia as a result of radiation to the head and neck during cancer therapy. The secondary objective is to use our improved understanding of hyposalivation to improve therapy for the large numbers in the general population who suffer from salivary malfunction. The overall objectives will be achieved over several years. The specific aims in the first year are as follows: 1. To relate the potential for demineralization in post-radiation patients to salivary flow rate, pH of saliva, inorganic constituents of saliva, and the ability of dental plaque to metabolize sugar to produce acid. 2. To study the changes in the organic acid composition of dental plaque attributable to fluoride therapy subsequent to radiation-induced Xerostomia. 3. To achieve a better understanding of the mechanism of fluoride action in these subjects and to suggest future regimes which can be tested to improve the preventive therapy. In subsequent years further specific aims will be as follows: 1. To elucidate the alterations in plaque acidogenesis and aciduricity following radiation-induced hyposalivation fluoride therapy, and to determine whether any changes observed are due to fluoride retention by plaque or to ecological shifts in plaque composition. 2. To examine the changes in concentration and presence of a specific 12,000 MW salivary protein during or post radiation. 3. To utilize the information learned to develop improved therapeutic regimes for easier and more effective management of radiation-induced xerostomia. 4. To apply the knowledge gained to the improved diagnosis and care of large numbers of subjects in the general population who have impaired salivary function. Use of this human model, combined with the animal model should greatly enhance our knowledge of the etiology, pathogenesis, and methods for the prevention of dental caries in the whole population.